mongocxx::stdx::optional<mongocxx::pool::entry> sc = try_get_connection_from_pool(connection_name);
    if (sc == mongocxx::stdx::nullopt) throw std::runtime_error("cant get connection from pool");
    mongocxx::client* conn = sc->get();

    try
    {
        auto db = (*conn)[connection_name];
        mongocxx::collection coll = db[collection];

        bsoncxx::document::value f = bsoncxx::from_json(json);

        mongocxx::options::find options;
        options.cursor_type(mongocxx::cursor::type::k_tailable_await);

        mongocxx::cursor cursor = coll.find(f.view(), options);

        while(is_running.load(std::memory_order_acquire))
        {
            /*if(cursor.begin() == cursor.end())
            {
                std::this_thread::sleep_for(std::chrono::seconds(1));
                continue;
            }*/

            //here its blocked
            for(auto&& doc : cursor)
            {
                mongo::db::fetcher st(doc);
                callback(&st);
            }

            if (callback_run) callback_run();
        }
    }
    catch(std::exception& ex)
    {
        throw ex;
    }